Cementitious binders and wood particles-based incombustible coloured composite panel with structural high performance

ABSTRACT

This invention relates to a composite panel made from wood and cementitious binders, with flat surfaces and several possible colours. The said panel comprises 35 to 85% of grey or white Portland cement; 10 to 30% of debarked resinous wood particles; 5 to 20% of semi-hydrated calcium sulphate; 0 to 10% of a surface accelerator; 0 to 10% of aluminium sulphate solution; 0 to 30% of calcium carbonate; and 0 to 15% of pigments. The invention uses the process of preparation for the existing VIROC panel, adjusting it to the new material. This panel, in addition to being very resistant and showing high performances in terms of resistance to impact, humidity, temperature variation, noise and fungi, as well as other microorganisms, also complies with all the requirements of the associated product standard.

FIELD OF THE INVENTION

This invention relates to a new type of incombustible cement wood, itsuse allowing an increased safety of the buildings against fire action,simultaneously providing the remaining properties of high durability,mechanical strength, acoustic behaviour and aesthetical interest, whichare usual for this kind of material.

It allows a wide variety of applications, from pavements, ceilings,roofings, to coating and insulation of building façades, and the like.

BACKGROUND OF THE INVENTION

Although the panels or coatings made from solid wood or wood derivativeshave a high bending strength, such as in the case of plywood, mediumdensity fiberboards (MDF) or particle boards (OSB), they also have a lowperformance in terms of water resistance, dimensional stability, inaddition to high susceptibility to attacks from fungi, insects andmicroorganisms, as well as low performance in what concerns its reactionto fire (in most cases with a classification equivalent to euroclass D).

The currently existing cement wood panels, which are commerciallyreferred to as “VIROC”, offer some advantages when compared to theaforementioned ones, since the mechanical performance and durabilitywere already guaranteed by the presence of Portland cement in theircomposition. However, their classification as regards the fire actiondoes not allow the degree of incombustibility to be achieved, beinggenerally rated with no more than Class B.

On the other side, the patent U.S. Pat. No. 6,221,521 B1 discloses aprocess wherein semi-hydrated or anhydrous gypsum is used and reinforcedwith organic fibers containing additives such as potassium sulphate, inorder to provide multilayer panels, and which is classified asincombustible according to ASTM E 136.

The patent U.S. Pat. No. 5,320,677 discloses another process wherein amixture of fluidized gypsum with cellulose fibers is heated underpressure, being then subject to cooling in order to produce a panel withthe desired conformation, although with a reference to gypsumcalcination.

The patent U.S. Pat. No. 5,342,566 is in line with the previous ones,however it comprises the use of light-weight fillers, such as perlite,combined with gypsum and cellulose fibers, for the production ofmultilayer panels. In the patent U.S. Pat. No. 5,135,805, thepossibility to use fibers of different origins is mentioned, such asglass or another mineral, and/or polypropylene in percentages rangingfrom 10 to 20%. All of these panels are considered incombustibleaccording to ASTM E 136, but their formula does not contain cement andthat is the reason why they have a limited scope of application,particularly in what concerns demands of a structural nature andexposure to outer environment.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem and DevisedSolution

The main advantage of the invention is based in the fact that it is anincombustible panel, without generating incandescent drops and with areduced smoke production, thus helping to minimize the risk of firedeflagration and propagation in the buildings and therefore contributingto an increased safety of people and property in case of fire.Simultaneously, it shows a good performance in terms of thermal andacoustic behaviour, resistance to impact, tensile and bending strength,resistance to humidity, as well as stability from the dimensional pointof view and resistance to fungi, insects and microorganisms, in additionto being economically competitive and very easily applied. Consideringall of these characteristics, it can be used in a wide variety ofdomains, inclusively with structural and architectural functions ininner and outer spaces.

Its composition is aimed at minimizing the incorporation of organicmatter in the form of wood chips in order to not compromise the panel'smechanical strengths (in special, the bending strength), and thecombination of the calcium sulphate in the form of semi-hydrate with thecement, according to the carefully determined proportions so as tocontrol eventual expansive reactions which might be generated, providesa very good behaviour as regards fire, causing the material to beincombustible. This new benefit significantly increases the scope ofapplication of the product and improves the behaviour of buildings underthe action of fire.

OBJECT OF THE INVENTION

Therefore, the object of this invention is an incombustible compositepanel of high performance, made of Portland cement, gypsum and woodparticles, comprising in weight percentage of the components withreference to the total weight of the composition:

1) 35 to 85% of grey or white Portland cement;2) 10 to 30% of debarked resinous wood particles;3) 5 to 20% of semi-hydrated calcium sulphate;4) 0 to 10% of a surface accelerator;5) 0 to 10% of aluminium sulphate solution;6) 0 to 30% of calcium carbonate; and7) 0 to 15% of pigments.

The resinous wood which is commonly used to obtain the component 2) ispinewood.

Preferably, the wood particles used therein are in the form of chips.

In general, the thickness of the said chips ranges from 0.25 to 0.32 mm.

In the preferred embodiments, 50 to 70% of the said chips, preferablyabout ⅔, are <1 mm long and 26 to 40%, preferably about ⅓, have a lengthof 1 to 4 mm.

Usually, the percentage of the component 3) is of about 11%.

Preferably, the surface accelerator being used as the component 4) is asodium silicate solution with a density between 1.10 and 1.15 g/cm³,wherein the sodium silicate has a SiO₂/Na₂O ratio between 3.19 and 3.53.

The aluminium sulphate which is used as the component 5), normally has adensity ranging from 1.05 to 1.10 g/cm³.

The calcium carbonate being used as the component 6) is generallylimestone filler, which is the result of the fine grinding of limematerials.

The pigments being commonly used as the component 7) are metal oxidepigments.

The composite panel according to the invention pertains to Class A incompliance with ASTM E 136 and to Class A2 in compliance with EN 13501-1and DIN 4102, having a good performance in terms of mechanicalstrengths, generally with a tensile strength under bending >9 N/mm² anda tensile strength perpendicular to the plane >0.5 N/mm², elasticitymodulus >4000 N/mm² and thermal conductivity <0.23 W/m².K.

Experimental Part

This formula aims both at minimizing the incorporation of wood chips andintroducing a mixture of binders with the incorporation of Portlandcement and semi-hydrated calcium sulphate, in order to ensure thecharacteristic minimum bending strength above 9 N/mm².

The cements used are grey or white Portland cements, depending on thedesired colour of the panel and according to the EN 197-1, which presentfast-developing strengths (designation “R” of the relevant standard).

The use of gypsum, in the form of semi-hydrated calcium sulphate incontrolled percentages, will not only provide the mixture with anacceleration of the setting process, but also an improvement of thepanel's thermal behaviour and fire resistance.

The wood chips used, which can be from pinewood or other resinous wood,are then broken and thinned to the following dimensions:

TABLE 1 Characteristics of the wood chips Length (mm) Thickness Fraction% <1 Fraction % Fraction % >4 (mm) mm [1;4] mm mm 0.25 and 0.32 50-7046-26 4

The use of sulphate of the aluminium type Al₂(SO₄)₃.nH₂O in a solutionwith a density ranging from 1.05 to 1,10 g/cm³ (1.07) allows the largerchips to be defibrillated, and the use of sodium silicate Na₂O.nSiO₂with a SiO₂/Na₂O ratio =3.19 to 3.53 in a solution with a densityranging from 1.10 to 1.15 g/cm³, will help both as regards theacceleration of the mixture's setting time and the mineralization of thewood chips.

The water to be used shall be clean (colourless and odourless),preferably drinking water, and free from oils or other impurities whichmight contaminate the colour of the concrete, so as to comply with theprovisions of the EN 1008.

The pigments suitable to the manufacture of the said mixture shall beinorganic and have the desired colour.

The manufacturing of the board is in accordance with the industrialprocess of the previously mentioned Viroc panel, in an appropriateinstallation. It comprises a wood treatment step, with debarking,cutting and defibrillation to the previously referred dimensions,followed by mixing of the constituents for at least 90s in an industrialmixer, followed by the conformation of the board using a conformationequipment, followed by pressing for the purposes of dimensionalstabilization. Subsequently, it is cured in a hardening chamber,air-matured and finally dried in a drying tunnel. After this, the plateis cut, rectified and packed.

EXAMPLES

The following are some of the possible examples regarding thepreparation of panels. These examples are designed to merely illustratethe invention, without in any way limiting the scope of the same.

Example 1

Panels were prepared with the following components and according to thestated dry weight percentages of material:

Step Component Weight % 1 Pinewood chips (⅔ <1 mm and ⅓ 15.4 [1;4] mm) 2Aluminium sulphate solution with 4.1 density of 1.07 g/cm³ 3 Sodiumsilicate solution with density 6.3 of 1.13 g/cm³ 4 Grey cement CEMII/A-L 42, 5R 62.8 5 Gypsum 11.5

Manufacturing Steps:

The logs of wood are reduced into chips. The latter are thinned anddivided into a group of larger chips with 1 to 4 mm and another group ofthinner chips with a thickness lower than 1 mm. The chips are introducedin the mixer wherein after 30 seconds half of the water required for theprocess is also introduced (this varying according to the equipmentused) and after another period of 30 seconds, the remaining portion ofwater is added. Again after 30 seconds, the aluminium sulphate isintroduced and then, after 60 seconds, the sodium silicate solution.

The cement and the gypsum are premixed for 60 s, and then added to theremaining constituents in the main mixer.

The mixture's conformation step is started, in which the said mixture isdistributed with an even thickness over steel plates, thus forming amattress. A stack of alternate plates and mattresses is formed with anumber of stages according to the thickness of the boards to bemanufactured. The stack is pressed and introduced in a hardeningchamber, in which, under the effect of pressure, temperature andhumidity and length of stay, it will gain the required strength in orderto be handled.

This set of boards is decompressed and the boards are separated from theplates. The panels are subjected to a precut operation and subsequentlythey are stacked and left to mature in a covered park. After maturation,the boards are introduced in the drying tunnel in order to remove theexcess moisture.

At the final step, the boards are cut to the desired size and treated inthe surface.

Example 2

According to the same process described in the Example 1, except in whatconcerns the calcium carbonate, which is processed together with thecement and the gypsum, panels were prepared with the followingcomponents and weight percentages:

Step Component Weight % 1 Pinewood chips (⅔ <1 mm and ⅓ 16.1 [1;4] mm) 2Aluminium sulphate solution with 4.3 density of 1.07 g/cm³ 3 Sodiumsilicate solution with density 5.8 of 1.13 g/cm³ 4 Grey cement CEM I42,5R 47.4 5 Gypsum 16.1 6 Calcium carbonate 10.3

Use of the Product of the Invention

The most common applications for this panel are:

Building façades:

The use of this type of panels in façades offers several benefits due tothe fact that it is a building material which can be used on outerspaces as well, with a good behaviour while enduring sun exposure, wetand dry cycles of rainwater, freeze and thaw cycles, and also due to itsacoustic and mechanical strengths, in addition to its easy applicationand workability, which enables it to be applied as is, or a finishingcan be adopted such as painting or coating with ceramic materials.

Walls:

Another possible application is for the purpose of building structuralor dividing walls, both in inner and outer spaces.

Its characteristics of mechanical strength, thermal strength andresistance to fire action, when applied with a support and fixingsystem, may represent a good solution.

In effect, the mechanical strength, durability and easy maintenance ofthe panels make them an excellent solution for the coating of innerspaces in buildings with high affluence of people (public buildings). Onthe other hand, inner wet areas can also be suitable spaces for usingthis type of panel due to its good behaviour concerning humidity, suchas in the case of bathing facilities and sanitary installations ingeneral.

Pavements:

The excellent features of mechanical strength, resistance to airbornesounds and percussion sounds, thermal strength, resistance to fireaction, as well as to fungi, termites and other microorganisms, allowthem to satisfy the specific requirements of pavements construction,when applied in an appropriate support system.

Ceilings:

Another possibility consists in the use of these panels as falseceilings, wherein excellent results can be obtained as regardsdurability and aesthetic aspects.

Roofings:

Being a non-deteriorable material when exposed to outer environments, itcan be used as the finishing final coating, which naturally requires theimplementation of a damp proofing system in order to ensure it remainswatertight.

Lost Formwork:

Its characteristics of rigidity, resistance and durability will allowthis panel to be used in the field of lost formworks.

Other Applications:

Interior decoration.

Sound barriers.

Street furniture and indoor furniture

Pallets

Characteristics of the Product of This Invention

The main characteristics of the product of this invention are listed inthe following table:

TABLE 2 Characteristics of the panels Characteristic Performance Density1500-1600 kg/m³ Thermal conductivity k = 0.23 W/m²·K Surface alkalinitypH = 11-13 Modulus of elasticity in bending  6000 MPa Tension parallelto the plane  5.00 MPa Tension perpendicular to the plane  0.60 MPaTension under bending  10.5 MPa Compression parallel to the plane  15.0MPa Compression perpendicular to the  40.0 MPa plane Transverse stress 2.00 MPa Water vapour diffusion resistance μ = 30 (wet method) factor μ= 50 (dry method) Fire Resistance A2-S1-d0 − EN 634.1/EN 13501-1/DIN4102-1 M0 − NF P 92-501 A − ASTM E136-1 Acoustic properties Soundreduction index Rw from 31 to 37 dB depending on thickness Soundabsorption coefficient α = 0.10 to frequencies of 250- 500 HzDimensional stability Maximum longitudinal and 0.7% between extremeamplitudes transverse variation of air relative humidity Thicknessvariation 1.5%—thickness variation after water immersion for 24 h

1. Incombustible composite panel of high performance, made from Portlandcement, gypsum and wood particles, characterized in that it comprises inweight percentage of the components with reference to the dry weight ofthe composition: 1) 35 to 85% of grey or white Portland cement; 2) 10 to30% of debarked resinous wood particles; 3) 5 to 20% of semi-hydratedcalcium sulphate; 4) 0 to 10% of a surface accelerator; 5) 0 to 10% ofaluminium sulphate solution; 6) 0 to 30% of calcium carbonate; and 7) 0to 15% of pigments.
 2. Composite panel according to claim 1,characterized in that the resinous wood used in order to obtain thecomponent 2) is pinewood.
 3. Composite panel according to claim 1 or 2,characterized in that the wood particles used as the component 2) are inthe form of chips.
 4. Composite panel according to claim 3,characterized in that the thickness of the said chips ranges from 0.25to 0.32 mm.
 5. Composite panel according to claim 3 or 4, characterizedin that 50 to 70% of the said chips are <1 mm long and 26 to 40% have alength of 1 to 4 mm.
 6. Composite panel according to any of the claims 1to 5, characterized in that the surface accelerator used as thecomponent 4) is sodium silicate solution with a density ranging from1.10 to 1.15 g/cm³.
 7. Composite panel according to claim 6,characterized in that the sodium silicate has a Si0₂/Na₂O ratio between3.19 and 3.53.
 8. Composite panel according to any of claims 1 to 7,characterized in that the aluminium sulphate used as the component 5)has a density between 1.05 and 1.10 g/cm³.
 9. Composite panel accordingto any of claims 1 to 8, characterized in that the pigments used as thecomponent 7) are metal oxide pigments.
 10. Composite panel according toany of claims 1 to 9, characterized in that it has a tensile strengthunder bending >9 N/mm², a tensile strength perpendicular to theplane >0.5 N/mm² and an elasticity modulus >4000 N/mm².
 11. Compositepanel according to any of claims 1 to 10, characterized in that itsthermal conductivity is <0.23 W/m².K.